1. The Field of the Invention
The present invention relates to cementitious insulation materials which can be used anywhere insulation may be needed. More particularly, the present invention is directed to laminate insulative structures which have one or more layers of a highly insulative material attached to a structural material including a cementitious structural matrix.
2. Related Applications
This application is a file-wrapper-continuation of copending application Ser. No. 08/027,451, now abandoned, entitled "Laminate Insulation Barriers Having a Cementitious Structural Matrix and Methods for Their Manufacture" filed Mar. 8, 1993, in the names of Per Just Andersen, Ph.D. and Simon K. Hodson, which is a continuation-in-part of co-pending application Ser. No. 07/929,898, entitled "Cementitious Food and Beverage storage, Dispensing, and Packaging Containers and the Methods of Manufacturing Same," filed Aug. 11, 1992, in the names of Per Just Andersen, Ph.D. and Simon K. Hodson (now abandoned), which is also a continuation-in-part of co-pending application Ser. No. 07/982,383, entitled "Food and Beverage Containers Made From Inorganic Aggregates and Polysaccharide, Protein, or Synthetic Organic Binders, and the Methods of Manufacturing Such Containers," filed Nov. 25, 1992, in the names of Per Just Andersen, Ph.D. and Simon K. Hodson (now abandoned). For purposes of disclosure, each of the foregoing applications is incorporated herein by specific reference.
3. Relevant Technology
From the beginning, man has labored against nature in his struggle to survive. Man has worked especially hard in the fight to stay warm--first by discovering that skins of beasts provided protection from the cold, and then by discovering that his dwelling place could be protected and insulated in like manner. As man built shelters to control his environment, he found that these structures, lean-tos, or huts made of wood, leaves, or reeds were effective as thermal barriers. As man progressed, he discovered that walls made with adobe, stone, or wood, and roofs made from grass or palm leaves, provided increased insulation. Even cork, where available, was used to insulate buildings.
In modern times, as mankind became more sophisticated, a wide variety of largely synthetic materials were developed which proved to be far superior insulators. However, with each step away from natural substances, mankind not only saw incremental improvements in the ability to insulate, but also huge increases in the environmental and health problems caused by various synthetic insulation materials.
A wide variety of inorganic and organic substances have been proven to cause grave health problems in humans, most notably asbestos and urea formaldehyde foam. In addition, many insulating foams used today are blown with chemical solvents known as chlorofluorocarbons (or "CFC's"), which have been implicated as being responsible for recent thinning in the ozone layer. Moreover, the best (i.e., the most insulative per unit of mass) synthetic insulation materials used today are organic foam materials, which tend to be flammable. When these organic foam materials burn, they often release extremely toxic fumes.
Another widely used insulation material, cellulose-based insulation made from shredded paper or other wood pulp products, is also highly flammable. In case of fire, these insulation materials not only will facilitate the incineration of the house, but will often expose the occupants of the house or building to deadly, or at least highly toxic, gases. Even fiberglass insulation, which is nonflammable, is often coated with certain organic-based (and flammable) materials to increase its workability. However, not even fiberglass insulations are completely fire resistant.
Generally, there are six basic types of thermal insulation: (1) air film or air layers; (2) closed cellular materials; (3) fibrous materials; (4) flake materials; (5) granular materials; and (6) reflective foils. Many applications may combine one or more of these insulation types.
Air films or air layers generally consist of a single surface, or a plurality of multiple surfaces, between which only air exists. An example of this is the double-paned or storm window. In addition, the simple shutter takes advantage to some degree of the air layer trapped between the shutter and the window being enclosed. Air layers are usually the safest forms of insulation, both from an environmental and health standpoint; the only variable is the material used to encapsulate the air.
Cellular insulation is composed of porous materials containing numerous small voids of air or gas. Generally, this material is of the closed cell variety, in which each cell is separated from the others by cell windows or thin membranes. Traditionally, cellular insulation has been produced from glass, plastics, and rubber. Common generic thermal insulations of this type are cellular glass, expanded elastomeric foam, polystyrene foam, polyisocyanate and polyurethane foams, and urea-formaldehyde foam. Except for cellular glass, these other forms of insulation are flammable and release toxic (and even deadly) fumes when ignited.
In addition, urea-formaldehyde foam insulation ("UFFI"), which became very popular in the 1970's during the energy crisis because of the ease in which it could be used to retrofit houses and buildings, has recently been implicated as causing numerous illnesses and respiratory problems. One notable and dangerous problem is that UFFI is known to release substantial quantities of formaldehyde over time.
Formaldehyde can be very toxic to humans, is irritating to mucous membranes, and is thought to be carcinogenic according to some experts. It is the major constituent of embalming fluid. Epidemiologic evidence indicates that adverse health effects associated with residential exposure to formaldehyde cover a wide range of signs and symptoms, including neurophysiological effects, eye and skin irritations, upper and lower respiratory irritations, pulmonary edema, and headaches. Rats exposed to only 15 ppm of formaldehyde developed squamous cell carcinoma in the nasal cavity.
As a result of the dangers relating to human exposure to UFFI, Canada and several states in the United States have banned the use of UFFI. Estimates of the number of homes insulated with UFFI are about 500,000 in the United States and about 100,000 in Canada.
Fibrous insulation is comprised of many small diameter fibers intertwined together to generally form open cell pockets of air between the bundles of fibers. These fibers can consist of organic materials such as hair, wood, and cane, or may be made from synthetic materials such as glass, rock wool, slag wool, aluminum silicate, asbestos, and carbon. Like the organic foams above, carbon fiber materials are highly flammable once ignited at high temperature. Except for asbestos, inorganic fibers are generally among the safest insulation materials, although they provide little or no structural support and must contain a shell made from metal foil or plastic in order to have a modicum of structural support.
On the other hand, asbestos, one of the most widely used insulation materials in the past, is proven to cause a number of severe (or fatal) health problems, including asbestosis and lung cancer. In addition, asbestos insulation workers often unwittingly ingest large quantities of asbestos, which has been shown to cause in these workers an increase in the incidence of colon cancer. In a study of 17,800 asbestos insulation workers, instead of 38.1 expected deaths due to cancer of the colon and rectum, there were 59. Seikoff, "Mortality Experience of Insulation Workers in the U.S. and Canada: 1943-1976," 330 Annals N.Y. Acad. of Sci. 91-116 (1979); see also Miller, "Asbestos Fiber Dust and Gastrointestinal Malignancies: Review of Literature with Regard to Cause/Effect Relationship," 31 J. Chronic Disorders 23-33 (1978).
Flake insulation materials consist of small particles or flakes which may be poured into an air space or bonded together to provide a rigid form of the insulation. Rigid form flake insulation can be used for pipe insulation or for other applications in block or board form. The two types of flake insulation commonly used are perlite and vermiculite. However, unless combined together in some kind of matrix, they are only useful as loose fill insulators.
Granular insulation is composed of small particles which contain voids or hollow spaces. These hollow spaces can transfer air between the individual voids. The parent material can be magnesia, calcium silicate, diatomaceous earth, or vegetable cork. The first three are commonly used as industrial pipe insulations, while cork is used in low temperature refrigeration applications.
Reflective insulation is composed of parallel thin sheets of foil with either high thermal reflectants or low emitants. These thin sheets are spaced to reflect radiant heat back to the source. Each separate sheet provides two heat transfer film coefficients; the air space between two sheets causes a reduction in conduction and convection. Foil insulation is commonly used in specially designed environmental chambers and in high temperature applications where radiative heat transfer is the predominant mode of heat transfer.
Another type of insulation material, more akin to the compositions and structures disclosed herein, is insulating concrete. Insulating and lightweight concretes are presently made by special methods, or by the addition of spongy aggregates. Slag may be used for this purpose. AEROCRETE.RTM. of the Aerocrete Corp., is a porous lightweight concrete produced by adding aluminum powder to the hydraulic cement. The aluminum flakes react with lime present within hydraulic cement to form hydrogen bubbles. DUROX.RTM. of the U.S. Durox Co., produced as lightweight blocks, panels, and wall units, is a foamed concrete made from a mixture of sand, lime, cement, and gypsum, along with aluminum powder which reacts to produce 3CaO.multidot.Al.sub.2 O.sub.3 and free hydrogen in the form of tiny bubbles. The set material contains about 80% cells and has only about 1/3 the weight of ordinary concrete with a compressive strength of 1,000 lb/in.sup.2 (6 MPa).
However, the insulating properties of the insulative concretes presently on the market are quite small relative to the insulation ability of the materials typically used in the building industry, like glass wool and organic foams. In addition, the available products are still very heavy compared to glass wool and organic foams. Hence, presently manufactured insulating concrete is limited in use and cannot take the place of conventional insulations used in the building industry or in the manufacture of appliances.
Nevertheless, insulating concretes have the advantage of being much safer than most of the insulation materials described above, and are more environmentally benign, since they are essentially comprised of the same components as the earth. In addition, they are fire resistant, nonflammable, and do not emit dangerous or toxic fumes when exposed to fire.
Besides the obvious health hazards of asbestos, UFFI, and ignited organic foams, certain organic foams, such as polystyrene and polyurethane/polyisocyanate foams, also pose grave environmental risks because they require the use of CFC's during their manufacture. They also consume vast amounts of petroleum, an ever diminishing resource, as the parent material.
As stated above, CFC's have been linked to the destruction of the ozone layer because they release chlorine products into the stratosphere. It is mainly due to the stability of CFC's that they do not soon degrade after first being emitted. Thus, they are allowed to migrate upward through the atmosphere until they reach the ozone layer in the stratosphere. Upon disintegration, it is believed that CFC's release chlorine, which is readily converted to chlorine monoxide, which in turn is thought to react with and destroy ozone.
Because the ozone layer acts as a filter to remove most of the harmful ultraviolet (or "UV") wavelengths emitted by the sun, it is believed that significant thinning of the ozone layer may, in the future, cause widespread damage to living organisms through excessive exposure to harmful UV light. In particular, excessive exposure to UV radiation causes sunburning of the skin of humans and animals, in addition to the burning of the retina. There have been numerous studies and reports that have concluded that further breakdown of the ozone layer may lead to sharp increases in skin cancer and cataracts in humans.
In the manufacture of foams, including styrofoam (or blown polystyrene), CFC's (which are highly volatile liquids) are used to "puff" or "blow" the polystyrene, which is then molded into the form of various insulating materials, including food and beverage containers. In particular, CFC-12 has been the agent of choice but is among the CFC's that have been slated to be phased out of use by 1996.
In addition to the chemicals used in the manufacture of insulation products, it is often necessary to dispose of used or scrap insulation itself, which most often ends up in municipal landfills. However, none of the traditional insulation materials is biodegradable except for cellulose-based products. Nevertheless, it is well documented that paper-based products (cellulose) persist for decades within landfills and do not decompose.
From the foregoing, it will be understood that what are needed are new forms of insulation which are not harmful, or which do not pose serious health risks, to the installer or the building dweller.
In addition, it would be a significant improvement over the prior art to provide insulation materials and methods for their manufacture which were more environmentally neutral and which do not use ozone-depleting chemicals. It would be a significant advancement to provide insulation materials with insulating properties comparable to asbestos, urea formaldehyde foam, or styrofoam, but which do not contribute to environmental or health problems.
Further, it would be appreciated that the alternative insulation material would be extremely useful if it could be produced at a cost equal to or even lower than currently used insulation materials. Further, it would be significant that such insulation materials might, in some cases, be both light-weight but have structural support comparable to typical gypsum board.
From a manufacturing perspective, it would be a significant advancement in the art to provide insulation barriers which can be rapidly formed while maintaining their shape without external support so that the barriers can be handled using conventional manufacturing techniques.
From a safety standpoint, it would be a substantial improvement over the prior art to provide insulation materials which were not only flame retardant, but that were completely nonflammable. It will be appreciated that it would be a major advancement to provide insulation materials which were not only fire resistant, but which also did not produce chemicals harmful to humans and, particularly, which did not cause lung or colon cancer, or asbestosis of the lungs.
It would be an important advancement if such insulation materials were more readily disposable than current insulation materials used in the construction of buildings, and which had essentially the chemical composition of the earth into which they might eventually be disposed.
Such insulation materials and barriers, along with methods for their manufacture, are disclosed and claimed herein.